The invention concerns methods in mammographic photography, wherein the breast to be photographed is pressed and spread between holders attached to the photographing apparatus, a beam of X-radiation being directed from one side of said holders through the breast placed between the holders at depicting means placed at the opposite side of the holders in relation to the source of X-radiation, the depicting means being placed inside a film cassette or equivalent placed in connection with the frame of the apparatus.
The invention further concerns mammographic apparatuses intended for carrying out the method of the invention, these apparatuses comprising a frame part, on which a turnable frame part is mounted, most preferably as to be turnable around a horizontal axis, and in which frame part a source of radiation and means for holding the film cassette as well as holders for the breast to be photographed, to be placed between the source of radiation and said cassette supporting means, are fitted, which breast holders are displaceable relative one another so as to press the breast to be photographed between said holders.
Mammography means a method of radioscopy of breasts, wherein a roentgenogram is taken of the breasts. In connection with the photographing, the breast is pressed and spread in a way known in the prior art between the holders in the photographing apparatus.
Owing to the nature of the tissue to be photographed, in the photographic method a relatively soft radiation is used, the anode voltage of the X-ray tube being about 20 . . . 28 kV. This results in problems of scattering, which are the more important become more serious, the thicker the tissue to be photographed is. In mammography, it is, however, be important to depict so-called microcalcifications, whose diameters are of an order of 0.1 mm.
As is known in the prior art, in complete mammographic photography, three different projections are used. In mass photography, only one, generally vertical, projection is used.
In addition to the roentgenograms taken in different projections, if necessary, enlarged photographs are taken of suspect locations.
Prior-art apparatuses can also be used for so-called biopsy photographing. Biopsy photography concerns a method wherein the breast is photographed by using a so-called biopsy plate so that the openings in the biopsy plate become visible in the roentgenogram. In biopsy photography, the film is developed while the breast to be photographed is kept in its holders, and the finding, if any, is located with the aid of the holes in the biopsy plate, and with their aid a sample is taken from a suspect location.
By means of the prior-art mammographic methods and apparatuses, it is also possible to take enlarged roentgenograms, which takes place such that a particular stand is placed on the normal breast holder, by means of which said stand the breast to be photographed is placed closer to the focus of the source of radiation. The use of such a separate stand is inconvenient, and, thus, one object of the present invention is to provide a new method and apparatus, wherein said separate stand becomes unnecessary.
In mammography, attempts are made to press the breast as flat as possible, because soft secondary radiation is scattered. The thinner the breast can be made, the less secondary radiation can be scattered. To prevent scattering, lattice solutions of various types are also used.
In respect of the prior art related to the present invention, reference is made by way of example to the mammographic apparatuses known from the following U.S. Pat. Nos. 3,824,297, 3,971,950, 4,097,748, 4,599,738, and 4,613,982.
The prior-art mammographic apparatuses have involved several drawbacks, which are eliminated in certain respects by means of the new solutions of the present invention.
One of the most important drawbacks has consisted of the difficulties in the operation of the prior-art apparatuses, these difficulties including the necessity of the patient ot move and to change her position when the projection or mode of photographing is changed, and it has been necessary to adjust the level of the breast holders in the apparatus between different processes of photography. This has increased the time taken by the photography, which is a considerable drawback in particular in the case of mass photography.
In the prior-art apparatuses, difficulties have also occurred in how to be able to press and to attach the breast to be photographed between the holders in the apparatus in a favorable way. The stage of pressing the breast, which is included in mammography, is often experienced by the patients as quite disagreeable, and as this stage has, in the prior-art apparatuses, often been associated with a necessity to readjust the breast to be photographed in a more advantageous position, this drawback has been experienced as quite embarrassing.